Wheels nut size

sorry if this is a really daft question… 

On all 4 of my wheels, 3 of my wheel nuts are 21mm socket size and 1 is 19MM. And looks different. It’s not a locking wheel nut. 

(Daft bit)…are the threads going to be all the same size. Does M12 x 1.5 sound familiar? And why is 1 different looking (longer)? 

When I looked at replacing them from ones on eBay (new) they all look the same and are the same size…?

Previous owner kept the lockers and put some available nuts on easy cure buy a set of lockers!!!

 

Ah ok, thanks. Did Mk1’s cme with locking nuts as standard do you know? 

Are the sizes I put above correct?